Iron and Vitamin C Supplementation in Pregnancy

Anand Viswanathan

I live in India. I do have friends living in Europe and the US. For once, something seems to be common in both the worlds- prescription of daily iron and vitamin supplementation for pregnant women. There is no doubt it is done with good intent, out of genuine health concerns. The problem is, such pills are not without their adverse effects. Ask anyone who has had, or known women who have had problems of excessive nausea/vomiting during pregnancy (hyperemesis), which is not uncommon; they would vouch against any pill that could cause nausea or vomiting.

Pregnant woman at home with Homepathic pills
image source: istock

What is the general belief?

Daily iron and vitamin C supplementation during pregnancy improves improves key pregnancy and birth related health outcomes for mothers and babies (anemia, birth-weight of the baby, still-birth etc).

What is the issue?

Iron and vitamin C supplementation could have adverse effects such as abdominal pain, and significant nausea/vomiting. Do benefits of these supplements outweigh the risk of adverse effects?

Is there scientific evidence about this?

Two recently updated Cochrane systematic reviews:

  1. Intermittent oral iron supplementation during pregnancy, 19 October 2015
  2. Vitamin C supplementation during pregnancy, 29 September 2015

What were the practically relevant questions asked in these reviews?

  1. Does ‘intermittent supplementation’ (two or three times a week on non-consecutive days) with oral iron tablets provide similar health benefits to the mother and the child, when compared to ‘daily supplementation’ during pregnancy? Are there lesser adverse effects (nausea) with ‘intermittent supplementation’?
  2. Does vitamin C supplementation improve pregnancy and birth related outcomes for the mother or the child?

What were the findings in these systematic reviews?

  • Iron supplementation review
    • 15 clinical trials, involving 5490 pregnant women from across the globe
    • ‘intermittent supplementation’ compared to ‘daily supplementation’ of oral iron tablets
    • Intermittent regimens produced similar maternal and infant outcomes as the daily regimens (anaemia, iron deficiency in women; infant birthweight, premature birth, and perinatal death)
    • Intermittent regimens were associated with fewer side effects (nausea, constipation)
    • Overall quality of evidence: low or very-low.
  • Vitamin C supplementation review
    • 29 clinical trials involving 24,300 pregnant women from 17 countries
    • Vitamin C supplementation versus Controls.
    • Routine supplementation with oral vitamin C tablets during pregnancy did not improve key health outcomes for women and their babies.
    • One study reported an increased risk of abdominal pain associated with vitamin C supplements.
    • Quality of evidence: moderate to high.

What did the authors conclude?

  1. Intermittent iron supplementation may be a feasible alternative to daily iron supplementation among those pregnant women who are not anaemic and have adequate antenatal care.
  2. Available data do not support routine vitamin C supplementation, alone or in combination with other supplements, for the prevention of fetal or neonatal death, poor fetal growth, preterm-birth, or high blood pressures (pre-eclampsia) in pregnant women.

What does this mean for pregnant women and their healthcare providers?*

  1. Healthcare providers could consider suggesting ‘intermittent supplementation’ instead of daily regimens of oral iron to suitable pregnant women, such as those who do not have anemia.
  2. Prescription of vitamin C supplementation during pregnancy to be considered only after weighing in the potential side effects, and the current evidence of lack of appreciable health benefits to mothers and infants.

*These blog posts are personal opinions of the author, and are not intended to be directly used as healthcare guidelines. Reader discretion, as always, is recommended.


1. Peña-Rosas JP, De-Regil LM, Gomez Malave H, Flores-Urrutia MC, Dowswell T. Intermittent oral iron supplementation during pregnancy. Cochrane Database Syst Rev. 2015;10:CD009997.
2. Rumbold A, Ota E, Nagata C, Shahrook S, Crowther CA. Vitamin C supplementation in pregnancy. Cochrane Database Syst Rev. 2015;9:CD004072.

Anand Viswanathan, a rehabilitation physician, currently works in a research position at Cochrane South Asia, Christian Medical College, Vellore- India. He is a firm believer in ‘shared decision making’  and ‘patient-centered clinical research’  being key to achieving optimal population healthcare. He could be reached at @anandtmc 

Cochrane is a global, not-for-profit, independent network of researchers, professionals, patients, carers, and people interested in health. Cochrane is engaged in gathering and summarizing the best evidence from research in the form of ‘Cochrane systematic reviews’, which represent an international gold standard for high quality, trusted information to make healthcare decisions better. Cochrane Systematic Reviews can be accessed free from anywhere in India, thanks to funding by the Indian Council of Medical Research.


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